• Nilendu Singh

      Articles written in Journal of Earth System Science

    • Radiation and energy balance dynamics over young chir pine (Pinus roxburghii) system in Doon of western Himalayas

      Nilendu Singh Bimal K Bhattacharya M K Nanda Prafulla Soni Jai Singh Parihar

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      The regional impacts of future climate changes are principally driven by changes in energy fluxes. In this study, measurements on micrometeorological and biophysical variables along with surface energy exchange were made over a coniferous subtropical chir pine (Pinus roxburghii) plantation ecosystem at Forest Research Institute, Doon valley, India. The energy balance components were analyzed for two years to understand the variability of surface energy fluxes, their drivers, and closure pattern. The period covered two growth cycles of pine in the years 2010 and 2011 without and with understory growth. Net short wave and long wave radiative fluxes substantially varied with cloud dynamics, season, rainfall induced surface wetness, and green growth. The study clearly brought out the intimate link of albedo dynamics in chir pine system with dynamics of leaf area index (LAI), soil moisture, and changes in understory background. Rainfall was found to have tight linear coupling with latent heat fluxes. Latent heat flux during monsoon period was found to be higher in higher rainfall year (2010) than in lower rainfall year (2011). Higher or lower pre-monsoon sensible heat fluxes were succeeded by noticeably higher or lower monsoon rainfall respectively. Proportion of latent heat flux to net radiation typically followed the growth curve of green vegetation fraction, but with time lag. The analysis of energy balance closure (EBC) showed that the residual energy varied largely within ±30% of net available energy and the non-closure periods were marked by higher rainspells or forced clearance of understory growths.

    • Differential behaviour of a Lesser Himalayan watershed in extreme rainfall regimes

      Pankaj Chauhan Nilendu Singh Devi Datt Chauniyal Rajeev S Ahluwalia Mohit Singhal

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      Climatic extremes including precipitation are bound to intensify in the global warming environment. The present study intends to understand the response of the Tons sub-watershed in Lesser Himalaya, in 3 years with entirely different hydrological conditions (July 2008–June 2011) in terms of discharge, sedimentflux and denudation rates. Within an uncertainty limit of ±20%, the mean interannual discharge (5.74 ± 1.44 m ³s ⁻¹) (±SE), was found highly variable (CV: 151%; 0.8–38 m ³s ⁻¹). In a normal rainfall year (2008–2009; ~1550 mm), the discharge was 5.12 ± 1.75 m ³s ⁻¹, whereas in a drought year (2009–2010), it reduced by 30% with the reduction in ~23% rainfall (CV: 85%). In an excessive rainfall year (once-in-a-century event) (2010–2011; ~3050 mm), discharge as well as total solid load was ~200% higher. Monsoon months (July–September) accounted for more than 90% of the annual solid load transport. The ratio of dissolved to suspended solid (C/P ratio) was consistently low (<1) during monsoon months and higher (1–7) during the rest of the dry period. C/P ratio was inversely (R ² = 0.49), but significantly (P<0.001) related to the rainfall. The average mechanical erosion rate in the three different rainfall years was 0.24, 0.19 and 1.03 mmyr ⁻¹, whereas the chemical erosion was estimated at 0.12, 0.11 and 0.46 mmyr ⁻¹, respectively. Thus, the average denudation rate of the Tons sub-watershed has been estimated at 0.33 mmyr ⁻¹ (excluding extreme rainfall year: 1.5 mmyr ⁻¹). Our results have implications to understand the hydrological behaviour of the Lesser Himalayan watersheds and will be valuable for the proposed and several upcoming small hydropower plants in the region in the context of regional ecology and naturalresource management.

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